(i) Field of the Invention
The present invention relates to a defective region processing apparatus and a defective region processing method for processing a defective region on an information storage medium including a plurality of regions, and an information storage device for recording information on the information storage medium.
(ii) Description of the Related Art
As a high-density information storage medium for recording/producing sound data or image data, an optical storage medium or magnetic storage medium are known. Spiral or concentric tracks are typically provided on such an information storage medium, and these tracks are divided into a plurality of regions which are generally called sectors. Information is stored by writing marks in these sectors by using a magnetic field or heat, and information is reproduced by reading the marks generated by the magnetic field or light.
A plurality of such sectors are provided on the information storage medium, and a defective sector may be generated during production or use of the information storage medium. An information storage device for recording information on an information storage medium or a formatting device for formatting an information storage medium is, therefore, provided with a function as a defective region processing device which executes a process for prohibiting use of such a defective sector or a process for registering a normal preliminary sector instead of such a defective sector.
With recent improvement in the computer technology, a data size or a quantity of sound data or image data to be used is increasing and enhancement of recording density of the information storage medium is eagerly desired. Miniaturization of the track pitch is demanded in order to greatly improve the recording density of the information storage medium.
As a technique for miniaturizing the track pitch, land and groove recording is proposed by which information is recorded on both flute-like grooves and protruding lands alternately provided on the storage medium.
FIG. 1 is a view showing sectors on an information storage medium adopting the land and groove recording.
FIG. 1 illustrates one groove 1 and two lands 2 and 3 sandwiching that groove. Both the groove 1 and the lands 2 and 3 are used as tracks, and a plurality of sectors are provided to each track. Numbers for differentiating the sectors are given to these multiple sectors. For example, the 10th sector Sct10, the 11th sector Sct11, the 12th sector Sct12, . . . are provided on the groove 1 depicted in this drawing, and the 0th sector Sct0, the first sector Sct1, the second sector Sct2, . . . , the 20th sector Sct20, the 21st sector Sct21, the 22nd sector Sct22, . . . are provided to the respective two lands 2 and 3 sandwiching the groove 1. That is, serial numbers are given to respective sectors provided in one track, and numbers given to a sector are different by 10 from those given to another sector adjacent to the former in a transverse direction of the tracks.
In this manner, both the grooves and the lands are used as tracks in the land and groove recording. The track pitch can be, therefore, simply reduced to approximately xc2xd as compared with a technique using only one of the grooves and the lands as tracks, and the recording density can be doubled if the linear recording density remains unchanged. Accordingly, the above-described technique is extremely important for realizing the high-density recording.
However, if the land and groove recording and the like is adopted to greatly miniaturize the track pitch, when reading a mark on a given track, cross talk caused due to a mark on a track adjacent to that track prevents the mark from being read. For example, when reading the mark recorded in the 11th sector Sct11 in FIG. 1, cross talk occurs due to the mark in the first sector Sct1 or the mark in the 21st sector Sct21.
FIG. 2 is a graph showing an example of cross talk.
The upper part in FIG. 2 shows a signal waveform 4 of a read signal obtained when performing reading with respect to an erased sector having no mark therein. A mark is written on a sector adjacent to the erased sector in a transverse direction of the tracks.
Further, the lower part of the FIG. 2 graph shows a waveform 5 of a gate signal indicative of a significant part in the read signal. In the signal waveform 4 of the read signal shown in the upper part of the graph, only a portion corresponding to a time interval during which the waveform 5 of the gate signal shown in the lower part rises is a significant signal waveform.
A flat waveform 4_1 and a spike-like waveform 4_2 exist in the signal waveform 4 of the read signal, and the flat waveform 4_1 is indicative of a signal caused due to an erased sector and the spike-like waveform 4_2 is indicative of cross talk owing to a sector on an adjacent track. The signal intensity of such cross talk may be strong such that the signal is hardly differentiated from an original read signal. In such a case, a mark is prevented from being read.
In the prior art defective region processing apparatus or defective region processing method, the above-described cross talk caused due to a defective sector keeps preventing a mark in a sector adjacent to the defective sector in the transverse direction of the tracks from being read even after a process for prohibiting use of the defective sector or a process for registering a normal preliminary sector instead of the defective sector is executed.
Although the above problem becomes prominent in an optical disk device adopting the land and groove recording, this problem occurs not only in such a device but it can be generally observed in an information storage device having the narrow track pitch.
In view of the above-described drawback, an object of the present invention is to provide a defective sector processing apparatus and a defective sector processing method capable of processing a defective sector so that a mark in a sector adjacent to the defective sector can be normally read, and an information storage device provided with a function as such a defective sector processing apparatus.
Since a mark can be normally read even though miniaturization of the track pitch is attained when the present invention is used, realization of high density of the information storage medium can greatly proceed.
To this end, a defective region processing apparatus according to the present invention comprises:
a mark writing section writing a mark onto an information storage medium which has a recording area divided into a plurality of regions, on which information is recorded by writing a mark in a region, and from which information is reproduced by reading the recorded mark;
a judging section making judgment upon whether a region having a mark written therein by the mark writing section is a normal region or a defective region; and
a recording state changing section changing a recording state of a mark in a region determined as a defective region by the judging section so that cross talk caused due to that region can be reduced.
The term xe2x80x9cregionxe2x80x9d used herein may be a generally called sector, a block consisting of a plurality of sectors, or multiple divided sectors.
In addition, the recording state changing section may change the recording state by using the mark writing section or may change the recording state by using means independent from the mark writing section.
Moreover, the defective region processing apparatus according to the present invention may be incorporated in an information storage device for recording information on an information storage medium or may be incorporated in a formatting device for formatting an information storage medium.
According to the defective region processing apparatus of the present invention, since the recording state of a defective region is changed so that cross talk due to that region can be reduced, a mark in a region adjacent to the defective region can be normally read.
The defective region processing apparatus according to the present invention, it is preferable that the recording state changing section erases a mark written in a region determined as a defective region by the judging section.
Erasing a mark in the defective region can readily reduce cross talk.
According to the defective region processing apparatus of the present invention, it is preferable that the recording state changing section overwrites a mark generating lower cross talk than cross talk due to a mark written in a region determined as a defective region by the judging section in that region.
Here, xe2x80x9ca mark generating lower cross talkxe2x80x9d may be a mark having a shorter length than an existing mark or may be a mark having a narrower width than an existing mark.
In order to reproduce information from an information storage medium, a plurality of regions including a defective region may be required to be sequentially scanned. In such a case, if a mark exists in that defective region, the stable scanning is enabled for the later-described reason.
It is to be noted that the mark having a narrower width than an existing mark can be easily realized by writing a mark with weaker power than the power used for writing an existing mark.
A defective region processing method according to the present invention for achieving the above-described object comprises:
mark writing step of a mark into a region on an information storage medium which has a recording area divided into a plurality of regions, on which information is recorded by writing a mark in the region, and from which information is reproduced by reading a recorded mark;
judging step of making judgment upon whether a region having a mark written therein by the mark writing step is a normal region or a defective region; and
recording state changing step of changing a recording state of a mark in a region determined as a defective region by the judging step so that cross talk caused due to that region can be reduced.
Furthermore, to achieve the above-described object, an information storage device according to the present invention for recording information onto an information storage medium which has a recording area divided into a plurality of regions, on which information is recorded by writing a mark in the region and from which information is reproduced by reading the recorded mark, comprises:
a mark writing section writing a mark onto the information storage medium;
a judging section making judgment upon whether a region having a mark written therein by the mark writing section is a normal region or a defective region; and
a recording state changing section changing a recording state of a mark in a region determined as a defective region by the judging section so that cross talk due to that region can be reduced.
Generally, in the information storage device, when recording of information is failed even though trial run of recording information with respect to a given region is repeated for a predetermined number of times, that region is determined as defective. When recording of information is failed in this manner, it is often the case that a mark indicative of incomplete information is written in that region, and cross talk caused due to such a mark is hardly differentiated from the original information. Reduction in cross talk according to the present invention is particularly effective.
Although only basic modes of the defective region processing method and the information storage device according to the present invention are disclosed herein in order to simply avoid tautological explanation, the defective region processing method and the information storage device include various types of defective region processing method and information storage device associated with each mode of the above-described defective region processing apparatus as well as the base modes of the defective region processing method and the information storage device.